Exhaust Treatment System Having Metal Hydride Module

ABSTRACT

An exhaust after-treatment system for treating an exhaust produced by an engine. The exhaust after-treatment system includes an exhaust passage, a catalytic exhaust after-treatment component in communication with the exhaust passage for treating the exhaust, and a metal hydride module in communication with the exhaust passage that receives a portion of the exhaust therein at a location positioned upstream from the catalytic exhaust after-treatment component. The portion of the exhaust that enters the metal hydride module reacts with a metal hydride contained in the metal hydride module to produce hydrogen gas that facilitates the treating of the exhaust by the catalytic exhaust after-treatment component.

FIELD

The present disclosure is directed to an exhaust after-treatment system including a metal hydride module.

BACKGROUND

This section provides background information related to the present disclosure which is not necessarily prior art.

Exhaust after-treatment systems generally include a catalyst-coated exhaust treatment component to treat the engine exhaust to remove harmful combustion by-products such as NOx, CO, and the like. During operation of the catalyst-coated exhaust treatment component, however, the catalyst surface can become poisoned by the formation of additional unwanted byproducts thereon due to, for example, nitrate-, sulfur- or phosphorus-based contamination. These byproducts can deactivate the catalyst, which reduces the efficacy of the engine exhaust after-treatment.

SUMMARY

This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

The present disclosure provides an exhaust after-treatment system for treating an exhaust produced by an engine. The exhaust after-treatment system includes an exhaust passage, a catalytic exhaust after-treatment component in communication with the exhaust passage for treating the exhaust, and a metal hydride module in communication with the exhaust passage that receives a portion of the exhaust therein at a location positioned upstream from the catalytic exhaust after-treatment component. The portion of the exhaust that enters the metal hydride module reacts with a metal hydride contained in the metal hydride module to produce hydrogen gas that facilitates the treating of the exhaust by the catalytic exhaust after-treatment component.

The present disclosure also provides an engine exhaust after-treatment system for treating an exhaust produced by the engine. The after-treatment system includes an exhaust passage including an exhaust treatment component therein, and a bypass passage including an inlet that receives a portion of the exhaust from the exhaust passage, a metal hydride module downstream from the inlet, and an outlet downstream from the metal hydride module that returns the portion of the exhaust to the exhaust passage. The module includes a metal hydride material that is configured to react with the exhaust and produce a hydrogen gas that is returned to the exhaust passage along with the portion of the exhaust. A valve is positioned at the inlet of the bypass passage that is configured to allow and prevent flow of the portion of the exhaust into the bypass passage, and a controller is in communication with the valve to open and close the valve. A sensor may be in communication with the controller, wherein the sensor is configured to send a signal indicative of an operating condition of the exhaust after-treatment system. Based on the signal indicative of the operating condition, the controller opens and closes the valve to control generation of the hydrogen gas by the metal hydride material.

Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

FIG. 1 is a schematic representation of an engine exhaust system according to a principle of the present disclosure;

FIG. 2 is a partial schematic representation of an exhaust after-treatment system according to an aspect of the present disclosure;

FIG. 3 is another partial schematic representation of an exhaust after-treatment system according to an aspect of the present disclosure;

FIG. 3A is a cross-sectional view of an exhaust passage including an co-axially aligned metal hydride module;

FIG. 3B is a cross-sectional view of any exhaust passage including a non-co-axially aligned metal hydride module;

FIG. 4 is another partial schematic representation of an exhaust after-treatment system according to an aspect of the present disclosure; and

FIG. 5 is another partial schematic representation of an exhaust after-treatment system according to an aspect of the present disclosure.

Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference to the accompanying drawings.

Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.

When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.

Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

FIG. 1 schematically illustrates a conventional exhaust system 10. Exhaust system 10 can include at least an engine 12 in communication with a fuel source (not shown) that, once consumed, will produce exhaust gases that are discharged into an exhaust passage 14 having an exhaust after-treatment system 16. Downstream from engine 12 can be disposed an exhaust treatment component 18 having a catalyst-coated substrate or filter 20, which can be any one of a diesel particulate filter (DPF), a diesel oxidation catalyst (DOC) component, a selective catalytic reduction (SCR) component, a lean NO_(x) catalyst (LNC), an ammonia slip catalyst (ASC), a three-way catalyst (TWC), a methane oxidation catalyst, a hydrocarbon-deNOx catalyst (HC-deNOx), or any other type of exhaust treatment device known to one skilled in the art. If a DPF is used, it may be catalyst-coated (e.g., SCR catalyst-coated). In the illustrated embodiment, substrate 20 includes a LNC component. Although only a single exhaust treatment component 18 is illustrated, it should be understood that exhaust after-treatment system 16 may include a plurality of exhaust treatment components 18 each including the same catalyst-coated substrate or filter 20, or where each exhaust treatment component 18 includes a filter 20 having a different catalyst.

Although not required by the present disclosure, exhaust after-treatment system 16 can further include components such as a thermal enhancement device or burner (not shown) to increase a temperature of the exhaust gases passing through exhaust passage 14. Increasing the temperature of the exhaust gas is favorable to achieve light-off of the catalyst in the exhaust treatment component 18 in cold-weather conditions and upon start-up of engine 12, as well as initiate regeneration of the exhaust treatment component 18 when the exhaust treatment substrate 20 is a DPF.

To assist in reduction of the emissions produced by engine 12, exhaust after-treatment system 16 can include a dosing module or injector 22 for periodically dosing an exhaust treatment fluid into the exhaust stream. As illustrated in FIG. 1, injector 22 can be located upstream of exhaust treatment component 18, and is operable to inject a suitable reagent. In the case of an LNC catalyst component as shown in FIG. 1, injector 22 can inject a hydrocarbon treatment fluid (e.g., ethanol, E85, ultra-low sulfur diesel fuel, or some other hydrocarbon or hydrocarbon mixture (such as an ethanol-gasoline blend)) into the exhaust stream. Injector 22 may receive the exhaust treatment fluid from a reagent tank 24 via a pump 26. The exhaust treatment fluid is fed by pump 26 through inlet line 28 to injector 22, and unused exhaust treatment fluid is routed back to tank 24 by return line 30. If exhaust treatment component 18 includes an SCR substrate, the reagent exhaust treatment fluid held by tank 24 may be an exhaust treatment fluid comprising urea. Flow of the exhaust treatment fluid through inlet line 28, injector 22, and return line 30 also assists in cooling injector 22 so that injector 22 does not overheat.

The amount of exhaust treatment fluid required to effectively treat the exhaust stream may vary with load, engine speed, exhaust gas temperature, exhaust gas flow, engine fuel injection timing, desired NO_(x) reduction, barometric pressure, relative humidity, EGR rate and engine coolant temperature. A NO_(x) sensor or meter 32 may be positioned downstream from LNC 20. NO_(x) sensor 32 is operable to output a signal indicative of the exhaust NO_(x) content to an engine electronic control unit (ECU) 34. All or some of the engine operating parameters may be supplied from ECU 34 via the engine/vehicle databus to exhaust after-treatment system controller 36. The controller 36 could also be included as part of the ECU 34. Exhaust gas temperature, exhaust gas flow and exhaust back pressure and other vehicle operating parameters may be measured by respective sensors, as indicated in FIG. 1.

Hydrogen aids in NOx conversion in a LNC system, and assists in reducing byproduct emissions that typically would require additional catalyst cleanup. Other systems that benefit from the use of hydrogen include NOx adsorbers, AMOx catalysts, three-way catalysts, and natural gas engine exhaust treatment systems. In this regard, the hydrogen may be used to regenerate the adsorber in a manner similar to a DPF (i.e., reduce soot), may be used to reduce light-off temperatures for the AMOx and three-way catalysts by as much as 10 C to 35 C, and may be used to reduce the light off temperature for methane combustion temperature in the natural gas engine exhaust system by as much as 80 C. Yet another benefit of hydrogen is that the hydrogen may be used for reaction with carbon dioxide for the generation of carbon monoxide or other on-board hydrocarbons such, for example, methanol, which may then be used in the exhaust treatment component 20 (such as a HC-deNOx catalyst), or to assist with dual fuel applications (e.g., engine applications that include more than a single fuel sources such as a ship or stationary application). The present disclosure, therefore, provides an exhaust after-treatment system 16 that includes a device configured to generate hydrogen to assist in treating the engine exhaust gases.

FIG. 2 illustrates a portion of an engine exhaust after-treatment system 16 according to a principle of the present disclosure. As illustrated in FIG. 2, exhaust passage 14 carries an engine exhaust including constituents such as oxygen (O₂), nitrogen (N₂), carbon dioxide (CO₂), water (H₂O) and nitrogen oxides (NO_(x)), amongst others. To remove NO_(x) from the exhaust stream, exhaust after-treatment system includes either an SCR catalyst or the lean NOX Catalyst (LNC) 20. Unfortunately, the catalyst of the SCR or LNC 20 can be negatively impacted by surface species that may deactivate the catalyst with respect to activity for NOx reduction. In particular, nitrates may form on the catalyst surface that can poison the catalyst.

To at least assist in preventing the formation of nitrates on the catalyst of the SCR or LNC 20, hydrogen gas can be used to facilitate the reduction of the surface nitrates on the catalyst of the SCR or LNC. According to the present disclosure, the hydrogen gas is generated using a metal hydride module 38 or canister that communicates with the exhaust passage 14. As shown in FIG. 2, metal hydride module 38 is positioned entirely within exhaust passage 14 such that a portion of the exhaust stream passes through metal hydride module 38 before reaching SCR or LNC 20. Metal hydride module 38 contains a metal hydride compound such as, for example, lithium hydride (LiH) that when brought into contact with water contained in the exhaust stream will produce at least one of a metal oxide (e.g., Li₂O), metal hydroxide (e.g., LiOH), and metal hydroxide hydrate (e.g., LiOH—xH₂O), and hydrogen gas. In particular, metal hydride module 38 includes one or more alkali and/or alkaline earth metal hydride components that react with the water vapor in the engine exhaust. The produced hydrogen gas exits the metal hydride module 38, intermixes with the remaining exhaust gases in exhaust passage 14, and then enters SCR or LNC 20 to facilitate the reduction of any nitrates that may have formed on the catalyst surface. In this manner, the removal of NO_(x) from the exhaust stream is enhanced by improved SCR and LNC performance.

It should be understood that because water is required for reaction within the metal hydride module 38, water must be present in exhaust passage 14. Thus, to ensure that water is present in the exhaust passage, exhaust after-treatment system 16 may include a water source 15 for injecting water or water vapor into the exhaust stream at a position located upstream from module 28.

Now referring to FIG. 3, a configuration similar to that illustrated in FIG. 2 is shown. The flow of exhaust into and out of metal hydride module 38, however, is controlled by valves 40. In this manner, the production of hydrogen gas is only conducted when required. Valves 40 may be in communication with controller 36 or ECU 34. Controller 36 or ECU 34, therefore, can control the opening and closing of valves 40 based on, for example, a signal indicative of the amount of NOx in the exhaust stream that is received from NOx meter 32. That is, if NOX meter 32 detects an increase in the amount of NOx downstream from SCR or LNC 20, the increase may be indicative of nitrates poisoning the catalyst of the SCR or LNC 20. Controller 36 or ECU 34, therefore, can then open valves 40 to allow the exhaust stream to enter metal hydride module 38 and generate hydrogen gas to facilitate the reduction of nitrates on the catalyst surface. Alternatively, controller 36 or ECU 34 can control valves 40 based on various engine operating conditions. For example, control of valves 40 can be dependent on whether engine 12 is running rich or lean, which can vary the amounts of various constituents in the exhaust stream. Regardless, it should be understood that valves 40 being in communication with controller 36 or ECU 34 allow the production of hydrogen dynamically in response to a plurality of different operating conditions.

Now referring to FIG. 3A, it can be seen that metal hydride module 38 may be mounted concentrically along axis A of exhaust passage 14. Alternatively, as shown in FIG. 3B, it should be understood that metal hydride module 38 can be offset from axis A. In this manner, a majority of the exhaust flow that typically flows along axis A can be allowed to enter metal hydride module 38 when module 38 is concentrically mounted, or a smaller portion of exhaust gas can be allowed to enter metal hydride module 38 when module 38 is mounted in the offset arrangement.

The portion 42 of exhaust passage 14 that carries metal hydride module 38 can be removable from exhaust passage 14. In this regard, the removal of the portion 42 of the exhaust passage 14 that carries metal hydride module 38 can be easily facilitated when metal hydride module 38 requires servicing. It should be understood, however, that exhaust after-treatment system 16 can be designed such that metal hydride module 38 can be expected to last significant amounts of time (e.g., periods of 2000 hours or more) that reduce the servicing required for metal hydride module 38. In addition, it should be noted that metal hydride module 38 may include a relief valve 41. Relief valve 41 allows for the escape of hydrogen gas from module 38 when valves 40 are closed. In this regard, if any residual water vapor from the exhaust stream remains in module 38 after closure of valves 40, the water vapor can react with the metal hydride therein to form hydrogen gas that is not allowed to otherwise escape module 38. Thus, if hydrogen gas is produced by module 38 after closure of valves 40, relief valve 41 allows the hydrogen gas to escape once a predetermined pressure threshold is reached. Although not illustrated, it should be understood that the metal hydride module 38 in FIG. 2 may also include a relief valve 41. The exhaust from pressure relief valve 41 may be directed to the exhaust passage 14 upstream or downstream of the metal hydride module 38 (e.g., into exhaust passage 14 near engine or near gas mixer 50), into the atmosphere, or elsewhere within the powertrain system where injection of hydrogen could be of practical benefit (e.g., routed to engine 12 to assist with combustion). Although not illustrated, it should also be understood that metal hydride module 38 may be connected to a vacuum source, such as a vehicle intake manifold, in order to remove a portion of the gaseous contents therein, and that the connection may include one or more valves and sensors.

It should also be understood that a suitable pressure sensor (not shown) may be installed within the metal hydride module 38. Then, if an excessive pressure rise occurs within the module 38 that is detected by the pressure sensor, valve 40 could be opened to release the gas into the exhaust stream to depressurize the metal hydride module 38.

Now referring to FIG. 4, an engine exhaust after-treatment system 16 including an exhaust passage 14 with an exhaust treatment component 20 therein is illustrated. Instead of positioning the metal hydride module 38 entirely within the exhaust passage 14, however, the exhaust passage 14 includes a bypass passage 44 including an inlet 46 that receives a portion of the exhaust from the exhaust passage 14, and the metal hydride module 38 is positioned within the bypass passage 44 downstream from the inlet 46. The bypass passage 44 also includes an outlet 48 downstream from the metal hydride module 38 that returns the portion of the exhaust to the exhaust passage 14. Similar to the above-described embodiments, the metal hydride module 38 includes a metal hydride material that is configured to react with the exhaust and produce a hydrogen gas that is returned to the exhaust passage 14 along with the portion of the exhaust.

A valve 40 is positioned at the inlet 46 of the bypass passage 44, which is configured to allow and prevent flow of the portion of the exhaust into the bypass passage 44. Further, similar to the above-described embodiments, a controller 36 may be in communication with the valve 40 to open and close the valve 40. A sensor (e.g., NOx meter 32 or a temperature sensor) is in communication with the controller 36. The sensor 32 is configured to send a signal indicative of an operating condition (e.g., NOx amounts or a temperature) of the exhaust after-treatment system 16, wherein based on the signal indicative of the operating condition, the controller 36 opens and closes the valve 40 to control generation of the hydrogen gas by the metal hydride material. Thus, the generation of hydrogen by module 38 can be controlled dynamically. Further, by exteriorly mounting metal hydride module 38 to exhaust passage 14, the servicing and replacement of metal hydride module and valves 40 can be easily facilitated. Although not illustrated, it should be understood that metal hydride module 38 may also include a relief valve 41.

Now referring to FIG. 5, it can be seen that exhaust after-treatment system 16 includes a metal hydride module 38 exteriorly mounted to exhaust passage 14. A bypass passage 44 including an inlet 46 that receives a portion of the exhaust from the exhaust passage 14 provides the portion of the exhaust to the metal hydride module 38, with the metal hydride module 38 being positioned within the bypass passage 44 downstream from the inlet 46. The bypass passage 44 also includes an outlet 48 downstream from the metal hydride module 38 that returns the portion of the exhaust to the exhaust passage 14. Similar to the above-described embodiments, the metal hydride module 38 includes a metal hydride material that is configured to react with the exhaust and produce a hydrogen gas that is returned to the exhaust passage 14 along with the portion of the exhaust.

An injector 28 configured to inject a hydrocarbon or exhaust treatment fluid comprising urea is positioned downstream from outlet 48. If exhaust treatment component 20 is an LNC, injector 28 is configured to inject hydrocarbon exhaust treatment fluid such as ethanol, ultra-low sulfur diesel fuel, or some other type of hydrocarbon into the exhaust stream to facilitate treatment of the engine exhaust. If the exhaust treatment component 20 is an SCR, the injector 28 is configured to inject fluid comprising urea into the exhaust passage 14.

It should be understood that a mixing device 50 can be located downstream from the metal hydride module 38 and upstream from the exhaust treatment component 20 to intermix the hydrogen gas and the exhaust. An exemplary mixing device is described in, for example, U.S. Pat. No. 8,397,495 assigned to Tenneco Automotive Operating Company Inc., which is hereby incorporated by reference in its entirety. Other mixing devices known to one skilled in the art, however, may be used without departing from the scope of the present disclosure.

The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure. 

What is claimed is:
 1. An exhaust after-treatment system for treating an exhaust produced by an engine, the exhaust after-treatment system comprising: an exhaust passage; at least one catalytic exhaust after-treatment component in communication with the exhaust passage for treating the exhaust; and a metal hydride module in communication with the exhaust passage that receives a portion of the exhaust therein at a location positioned upstream from the catalytic exhaust after-treatment component, wherein the portion of the exhaust that enters the metal hydride module reacts with a metal hydride contained in the metal hydride module to produce hydrogen gas that facilitates the treating of the exhaust by the catalytic exhaust after-treatment component.
 2. The exhaust after-treatment system according to claim 1, wherein the catalytic exhaust after-treatment component is a diesel particulate filter, a gasoline particulate filter, a SCR exhaust treatment component, a NOx storage catalyst component, a hydrocarbon storage catalyst component, a LNC exhaust treatment component, a diesel oxidation catalyst component, a methane oxidation catalyst component, a three-way catalyst component, an ammonia slip catalyst component, or a combination thereof.
 3. The exhaust after-treatment system according to claim 2, wherein the catalytic exhaust after-treatment component is the LNC exhaust treatment component.
 4. The exhaust after-treatment system according to claim 1, wherein the metal hydride module is mounted entirely within the exhaust passage.
 5. The exhaust after-treatment system according to claim 1, further comprising a bypass passage in communication with the exhaust passage that receives the portion of the exhaust, the metal hydride module being positioned within bypass passage.
 6. The exhaust after-treatment system according to claim 1, wherein the metal hydride module includes a valve configured to allow entry of the portion of the exhaust into the metal hydride module.
 7. The exhaust after-treatment system according to claim 6, further comprising a controller in communication with the valve that is configured to open and close the valve.
 8. The exhaust after-treatment system according to claim 1, further comprising a mixing device configured to intermix the hydrogen gas and the exhaust, the mixing device being positioned in the exhaust passage between the metal hydride module and the catalyst exhaust treatment component.
 9. The exhaust after-treatment system according to claim 1, further comprising an injector for dosing an exhaust treatment fluid into the exhaust passage.
 10. The exhaust after-treatment system according to claim 9, wherein the exhaust treatment fluid is a hydrocarbon exhaust treatment fluid or an exhaust treatment fluid comprising urea.
 11. The exhaust after-treatment system according to claim 10, wherein the hydrocarbon exhaust treatment fluid is ethanol, an ethanol-gasoline mixture, or an ultra-low sulfur diesel fuel.
 12. The exhaust after-treatment system according to claim 1, wherein the metal hydride module includes a relief valve.
 13. The exhaust after-treatment system according to claim 1, wherein the metal hydride contains at least one component selected from the group consisting of an alkali metal hydride component, an alkaline earth metal hydride components, and combinations thereof.
 14. An engine exhaust after-treatment system for treating an exhaust produced by the engine, the after-treatment system comprising: an exhaust passage including at least one exhaust treatment component therein; a bypass passage including an inlet that receives a portion of the exhaust from the exhaust passage, a metal hydride module downstream from the inlet, and an outlet downstream from the metal hydride module that returns the portion of the exhaust to the exhaust passage; a metal hydride material within the metal hydride module configured to react with the exhaust and produce a hydrogen gas that is returned to the exhaust passage along with the portion of the exhaust; a valve positioned at the inlet of the bypass passage configured to allow and prevent flow of the portion of the exhaust into the bypass passage; and a controller in communication with the valve, the controller configured to open and close the valve; and a sensor in communication with the controller, the sensor configured to send a signal indicative of an operating condition of the exhaust after-treatment system, wherein based on the signal indicative of the operating condition, the controller opens and closes the valve to control generation of the hydrogen gas by the metal hydride material.
 15. The exhaust after-treatment system according to claim 14, wherein the catalytic exhaust after-treatment component is a diesel particulate filter, a gasoline particulate filter, a SCR exhaust treatment component, a NOx storage catalyst component, a hydrocarbon storage catalyst component, a LNC exhaust treatment component, a diesel oxidation catalyst component, a methane oxidation catalyst component, a three-way catalyst component, an ammonia slip catalyst component, or a combination thereof.
 16. The exhaust after-treatment system according to claim 15, wherein the catalytic exhaust after-treatment component is the LNC exhaust treatment component.
 17. The exhaust after-treatment system according to claim 14, further comprising a mixing device configured to intermix the hydrogen gas and the exhaust, the mixing device being positioned in the exhaust passage between the metal hydride module and the catalyst exhaust treatment component.
 18. The exhaust after-treatment system according to claim 14, further comprising an injector for dosing an exhaust treatment fluid into the exhaust passage.
 19. The exhaust after-treatment system according to claim 18, wherein the exhaust treatment fluid is a hydrocarbon exhaust treatment fluid or an exhaust treatment fluid comprising urea.
 20. The exhaust after-treatment system according to claim 19, wherein the hydrocarbon exhaust treatment fluid is ethanol, an ethanol-gasoline mixture, or an ultra-low sulfur diesel fuel.
 21. The exhaust after-treatment system according to claim 14, wherein the metal hydride module includes a relief valve.
 22. The exhaust after-treatment system according to claim 14, wherein the metal hydride material contains at least one component selected from the group consisting of an alkali metal hydride component, an alkaline earth metal hydride component, and combinations thereof. 